1. Field of the Invention
The invention concerns a method for fitting a top or a bottom to the body of a can, by internal rolling; it also concerns a machine for executing this method.
2. Description of the Prior Art
Many cans, at least partly in metal, are made by peripheral crimping forming a bead projecting circumferentially at the ends of the can. This bead is an area especially sensitive to corrosion (formation of rust when the can is left in a moist place, such as a bathroom, for example). Also, the esthetic result is poor, which may constitute a disadvantage for some articles such as perfumery products sold in aerosol type containers. In this specific area where the decoration of the packaging is important to promoting the product the presence of the bead interrupts the decoration and emphasizes in an unesthetic way the end of the package. Also, because the crimping process is applied after the body of the can is decorated by painting and varnishing it, known crimping tools damage the coating, which is one reason for the vulnerability of this area to corrosion. Finally, the presence of the external bead prevents stacking of such metal packages, which raises problems for storing and handling them.
Attempts have been made to produce an internal, non-projecting crimp, as evidenced by U.S. Pat. No. 3,452,897, for example. At the time of writing, however, there would not seem to have been any industrial exploitation of this type of crimp. Furthermore, using it entails soldering before the operations which lead to the formation of the internal crimp, which substantially increases manufacturing costs.
The invention makes it possible to remedy these disadvantages by proposing a new method of fitting a top or a bottom to the body of a can producing an internal crimp with no bead projecting from the periphery of the corresponding end of the can. The basic idea of the invention is to use a rolled edge preformed on said top or bottom as a support or reaction surface during internal rolling of the end portion of the can body.